In recent years, various methods for manufacturing an antireflective film which is a film-shaped antireflective article by arranging a number of fine protrusions closely to each other on the surface of a transparent base (transparent film) to prevent reflections have been proposed (see Patent Documents 1 to 3). These methods utilize the properties of a so-called moth-eye structure to change the refractive index to incident light continuously in a thickness distribution of a substrate to eliminate interfaces where the refractive indexes are discontinuous to thereby prevent reflections.
In an antireflective article having this moth-eye structure, fine protrusions are arranged closely to each other so that an interval d between adjacent fine protrusions is no more than a shortest wavelength Λmin of a wavelength band of electromagnetic waves of which reflections are to be prevented (d≦Λmin). Moreover, each fine protrusion is manufactured so that the fine protrusion stands vertically on the transparent base and the cross-sectional area thereof decreases (the fine protrusion is tapered) as the fine protrusion advances from the transparent base toward a distal end.
Various applications of the antireflective article have been proposed. For example, the antireflective article may be disposed on a light emission surface of various image display devices to reduce reflections of external light such as sunlight from the screen to improve visibility of images. Further, a touch panel may be formed using electrodes in which a fine protrusion group is formed on a sheet-shaped or planar transparent base and a transparent conductive film such as ITO (indium-tin oxides) on the fine protrusion group. By doing so, it is possible to prevent optical reflections between the touch panel electrodes and various members adjacent to the electrodes to suppress the occurrence of interference patterns or ghost images.
Moreover, Patent Document 4 discloses this type of antireflective articles which can secure a sufficient anti-reflection function even when a plurality of peaks is formed at an apex of a fine protrusion due to the resin filling defects during molding.
However, an antireflective article having this type of moth-eye structures has a problem in that the scratch resistance thereof is not sufficient for practical use. That is, for example, when another object comes into contact with the antireflective article, the anti-reflection function deteriorates in a local region, and cloudy spots, scratches, or the like appear in the contacting region, which may cause appearance defects.
Patent Document 1: Japanese Unexamined Patent Application, Publication No. S50-70040
Patent Document 2: Japanese Unexamined Patent Application (Translation of PCT Application), Publication No. 2003-531962
Patent Document 3: Japanese Patent No. 4632589
Patent Document 4: Japanese Unexamined Patent Application, Publication No. 2012-037670